1. Field of the Invention
The present invention relates to an alignment method of nozzle heads, a line head, and an ink jet recording apparatus mounted with its line head.
2. Description of Related Art
An effective measure for speed-up of a printing speed in an ink jet recording apparatus is to provide a line head having a length of a printed width region (for example, width of A4). However, at present when printing of 1200 to 4800 dpi resolution becomes the main current, it is very difficult to arrange nozzle holes at the necessary pitch throughout the length of the printed width region. Namely, in case of a line head having the length of A4 width (210 mm), the number of printing pins per color is over several thousand. Therefore, integration of all or integration of only a nozzle plate, taking into account the possibility that bad printing is produced, is not efficient.
Therefore, a line head has been proposed, for example, in Japanese Patent No. 3302785, in which nozzle heads each having the comparatively small area at hundreds pin-levels are combined and arranged.
In Japanese Patent No. 3302785, technology that nozzle holes are gathered in such a line head has been disclosed. Specifically, an ink jet recording apparatus has been disclosed, which is a full-line type recording apparatus that has plural ink jet recording head units having plural recording elements and plural ink ejection ports arranged in at least one row correspondingly to the recording elements, and in which the ejection ports of the plural ink jet recording heads are arranged throughout the entire width of a recording region of a recorded medium. This ink jet recording apparatus includes a common ink jet recording unit holding means which detachably holds the plural ink jet recording heads. The plural ink jet recording head units tilt at a predetermined angle relative to a transporting direction of the recording medium. Further, on the common ink jet recording head unit holding means, its attachment surface of the ink jet recording head unit is practically formed stepwise. The ink jet recording head units are attached on the stepwise attachment surface of the common ink jet recording head unit holding means from the same direction, and the ink ejection port located in the same position of each ink jet recording unit is positioned and held on a straight line that is orthogonal to the transporting direction of the recording medium.
Here, the main current of the present ink jet is a face shoot type. However, the proposed line heads are almost an edge shoot type in which a nozzle plate is elongated. This is because nozzle density viewed from a nozzle surface can be made large in the edge shoot type.
Regarding the nozzle density, not only the nozzle holes on the nozzle surface are taken into consideration but also an energy generating source, a flowing path, a mounting part, an ink supply part, distance from an edge of the nozzle plate to the nozzle hole, all the parts must be efficiently combined, unless the nozzle density, that is, resolution cannot be improved.
However, the edge shoot type, since the number of dimensions requiring accuracy becomes large due to its structure, requires a high level of accuracy in the manufacture of the head. Further, since only one array of nozzle holes can be basically arranged, in a case where a minimum necessary distance from the nozzle plate edge to the nozzle hole is secured, the nozzle density is not always increased.
Namely, in a case where the width of the nozzle plate is narrowed and the distance from the edge of the nozzle plate to the nozzle hole is shortened in order to increase the nozzle density when the line head is used, not only is a purge cap for preventing clogging of the nozzle hole difficult to place, but also the nozzle plate becomes elongated thereby readily causing warping. Further, in a case where the nozzle plate is formed long thereby to increase the number of the nozzle holes arranged in one row in order to increase the nozzle density, not only the warp is easy to be produced since the nozzle plate becomes long, but also an influence of pitch shift is great due to the long plate.